Compressor turbine



4 Sheets-Sheet 1 Filed Sept. 17, 195 9 June 5, 1962 E. DENT ETAL3,037,742

COMPRESSOR TURBINE Filed Sept. 17, 1959 4 Sheets-Sheet 2 IN V! N TOPSATTORNEY June 5, 1962 T ETAL 3,037,742

COMPRESSOR TURBINE Filed Sept. 17, 1959 4 Sheets-Sheet 3 INVENTORS Y A MATTORNEY June 5, 1962 E. DENT ETAL COMPRESSOR TURBINE 4 Sheets-$heet 4Filed Sept. 17, v1959 United States Patent 3,037,742 COMPRESEOR TURBINEEugene Dent, Indianapolis, Ind., and Robert E. Weiser,

San Diego, Calif., assignors to General Motors Corporation, Detroit,Mich., a corporation of Delaware Filed dept. 17, 1959, Ser. No. 841,9217 Claims. ((11. 253-77) This invention relates to the rotors ofturbomachinery, more particularly to a two-tier coaxial blade rotorconstruction for a gas turbine power plant wherein the outer tiercomprises turbine blading, and more specifically to an improved shroudconstruction intermediate the two tiers of blading.

In a gas turbine power plant of the type described, the shroudintermediate the two tiers of blades not only serves to support theWidely spaced outer tips of the compressor blading and the peripheralturbine blading, but further improves the efiiciency of the axial flowcompressor, acts as a sealing means between the gas turbine and thecompressor chambers and further constitutes a thermal barriertherebetween. The provision of such a shroud involvcs considerablediifculty in the design and assembly of such a rotor, however. Thespacing of the compressor blade tips and the turbine blades must beaccurately maintained with respect to such a shroud and the associatedstructure. As the rotational speed of such a rotor is relatively high,the shroud must also be designed to withstand the necessarily highcentrifugal forces acting thereon. In most cases, however, it isparticularly important that the structure of the rotor be kept as lightas possible. If the shroud is heavy, it not only contributes unnecessaryweight directly to the rotor structure but it may also require a heavierdisk to withstand the additional centrifugal force imposed thereon bythe shroud mass. It is therefore desirable that the rotor shroud be madeas light as possible but have suflicient strength to withstand thecentrifugal forces acting thereon.

The invention contemplates an improved lightweight shroud structurewhich may be easily and economically fabricated and to which thecompressor blade tips and the turbine blades may be easily and securelyattached to provide a relatively light coaxial blade rotor structure ofextremely high strength.

The foregoing and other objects, advantages and features of theinvention will be apparent to those skilled in the art from thefollowing detailed description of two preferred embodiments thereofhaving reference to the accompanying drawings, in which:

FIGURE 1 is a fragmentary rear view of a portion of a two-tier, coaxialturbine-compressor rotor embodying a first form of the invention, theview being taken in a plane perpendicular to the axis of the rotor;

FIGURE 2 is a fragmentary perspective view of a portion of the rotorshown in FIGURE 1 and shows details of the shroud and blade structure inbroken-away section;

FIGURE 3 is a fragmentary perspective view showing the tip of one of thecompressor blades as used in the form of the invention shown in FIGURE1;

FIGURE 4 is a fragmentary view showing the mounting of the turbineblades on the shroud structure in a peripheral elevation or developmentof the rotor of FIG- URE 1;

FIGURE 5 is a fragmentary sectional view showing a second form oftwo-tier, coaxial turbine-compressor rotor stage embodying the inventionwith portions thereof broken away and in section to show the details ofconstruction, the primary section of the view being taken in a planeincluding the axis of the rotor; and

FIGURE 6 is a fragmentary perspective view of a portion of the rotorshown in FIGURE 5 showing further details of this form of the inventionin broken-away section.

Referring first to FIGURE 1, which sufiiciently illustrates a compressorrotor structure incorporating the in vention, the rotor comprises arotor disk or Wheel 10, only a portion of the periphery of which isillustrated. The periphery of the wheel includes a rim 11 having aplurality of equiangularly spaced dovetail slots 12 therein extendinglongitudinally across the rim or, in other words, axially of the rotor.The dovetail slots 12 serve to mount a ring or row of compressor blades13 which extend radially from the rim of the rotor. Each blade comprisesan airfoil or blade portion 14, a platform 15, a stalk 16 and a root 17which is configured to fit one of the dovetail slots 12. Since theplatform and blade are of greater axial extent than the root, webs 18extend obliquely from the faces of the root and stalk to the undersideof the platform. The blade platforms engage along their edges to providea frusto-conical ring defining the inner boundary of the air flow paththrough the compressor. An interrupted flange 19 extends radiallyoutwardly from the rim 11 between the stalks to the inner surfacesdelined by the platforms 15 and provides a sealing means preventing airleakage between the inlet and discharge sides of the rotor.

It will be noted that the compressor blades are relatively long andwidely spaced at their tips. The compressor blades are also disposed ata considerable angle or skewed to the rotor axis, which is perpendicularto the plane of FIGURE 1. As seen in FIGURES 2 and 3, the tips of thecompressor blades are notched to provide a plurality of prongs ordovetail projections 20 which define a plurality of equally spacedparallel side face portions which are normal to the rotor axis. Thesepronged ends of the compressor blades mount a shroud ring 21.

In accordance with the invention, the shroud ring 21 is of a brazedfabricated sheet metal construction comprising an inner sheet metal band22, the outer sheet metal band 25, and an intermediate corrugated sheetmetal band 27 sandwiched there'oetween. The inner band 22 is ofchanneled cross-section facing outwardly and providing two axiallyspaced, radially extending seal flanges 23 interconnected by an annularbase section 24. The outer sheet metal band 25 is of oppositely disposedchanneled cross-section and is nested within the channel of the innerband 22, having two inclined end fiages 26 which extend obliquely andinwardly from an outer base section 30 and are secured by brazing to thebase portion 24 of the inner band immediately adjacent the seal flanges23. The intermediate corrugated band 27 is of rectangularly sinuouscross-section defining a number of intermediate radial webs 28 and twooutwardly extending radial webs 28 at opposite ends thereof. The innerand outer ends of the webs 28 and 28 are joined by axially extendingwebs 29 and 29' which are brazed to the base sections 24 and 30 of theinner and outer shroud bands, respectively. The outer peripheries of thetwo end webs 28 are also brazed annularly to the outer band flanges 26thus reinforcing these flanges and increasing the overall stiffness ofthe shroud assembly.

The annular base section of the inner band 22 is provided with a numberof openings or cutouts 31. These cutouts mate with the inwardly facingchannels defined by the radial webs 28 and are disposed to receive thedovetail prongs 20 of the several compressor blade tips during assemblyof the rotor. When thus assembled, the oppositely disposed side faceportions of the several prongs engage the mating faces of the radialwebs 28 of the shroud assembly. The dovetail joints thus formed betweenthe pronged tips of the several compressor blades and the shroud ringare then preferably brazed securing the prongs 20 to the radial webs 23and securing the tips of the several compressor blades to the inner band22. It will be seen that this shroud construction is of extremely lightweight but when integrated by brazing to the several compressor bladetips is of sufiicient strength and rigidity to withstand the centrifugalforces acting thereon and to maintain the angular spacing of the severalcompressor blade tips.

The lightweight shroud construction described above is furtherreinforced by mounting an outer tier of hollow turbine blades 32circumferentially thereon. The turbine blades 32 may be suitablyfabricated from sheet metal stock or may be hollow cast and subsequentlymachined or otherwise formed to the desired configuration. In the formof the invention shown in FIGURES 1-4, each turbine blade is secured tothe shroud assembly by means of a flanged root element 33. Each rootelement 33 is suitably formed from sheet metal stock to provide a firstbase flange 33 mateable with and brazed to the circumferential surfaceof the shroud section and a second flange 33" extending outwardlytherefrom. The outwardly extending flange of each root or blade mountingelement is embraced by and brazed to the radially inner end of itsassociated turbine blade. As best seen in FIG- URE 4, the severalturbine blades 32 and their respective flanged root elements 33 overlapcircumferentially of the shroud 21 and serve to further increase theoverall strength and rigidity of the shroud construction while whileminimizing the additional mass carried thereby.

The rotor illustrated in FIGURES S and 6 differs from that of thepreviously described embodiment in that it is of somewhat greatercompressor capacity and consequently includes two rows of outer bladingwhich are axially spaced and cooperate with stator blading or nozzlemeans to provide a two-stage turbine. With respect to the invention,however, this embodiment differs primarily in the structure of theshroud ring and the mounting of the several turbine blades thereon.

In this form of the inventon, the shroud ring indicated generally at 34comprises a fabricated annular sheet metal portion 35 which extendsaxially between two spaced end seal rings 36. These end rings may becast or otherwise suitably formed. The fabricated sheet metal portion ofthe shroud 34 comprises three radially spaced concentric cylindricalsheet metal bands 37, 38 and 39. Two corrugated sheet metal bands and 41are sandwitched between the cylindrical bands 37 and 38 and between thebands 38 and 39, respectively. As in the preceding embodiment, thesecorrugated bands 40 and 41 are of rectangularly sinuous cross-sectionand thus define a number of radial webs 42 and 43, respectively, whichare joined by axially extending Webs 44, 44' and 45, 45, respectively.The axially extending webs 44 and 44 are brazed to the inner andintermediate circular bands 37 and 38, respectively, and the axial Webs45, 45 of the outer corrugated band 41 are similarly brazed to theintermediate and outer circular bands 38 and 39, respectively. The endrings 36 are each provided with two concentric flanges 46 and 47. Theopposite ends of the inner circular band 37 and the adjacent radial endwebs 42 of the corrugated band 40 are brazed to the inner end ringflanges 46. The outer end ring flanges 47 are similarly brazed to theadjacent ends of the outer circular band 39 and of the radial end webs43 of the corrugated band 41. The opposite ends of the intermediatecircular band are also brazed to the end rings 36 intermediate the innerand outer flanges 46 and 47 thereof.

A in the preceding embodiment, the inner band 37 is provided with anumber of cutouts 48 which open on the inwardly facing channels definedby the inner corrugated band 40. These cutouts are disposed and adaptedto receive the dovetailed pronged tips 49 of compressor blades 50. Uponassembly of the shroud on the tips of the compressor blades, as in theprevious embodiment, the pronged tips 49 of the compresor blades aresecured by brazing to the radial webs 42 of the inner corrugated band 40and to the inner cylindrical band 37 to provide an integrated lightWeight shrouded rotor structure of relatively high strength.

In this embodiment of the invention, the turbine blades 51 are securedto the shroud assembly in the same manner as the compressor blade tips,the radially inner ends of the turbine blades being provided with aplurality of dovetail prongs 52. These prongs are insertable throughcutouts 53 which are provided therefor in the outer cylindrical band 39and open on the outwardly facing channels defined by the radial webs 43of the outer corrugated band 41. When the turbine blades have been thusassembled on the periphery of the shroud, the prongs 52 and the radiallyinner ends of the turbine blades are secured by brazing to theintermediate and outer circular bands 38 and 39 and the intermediatecorrugated band 41 thereby further reinforcing the relativelylightweight shroud structure.

From the foregoing it will be seen that the invention accomplishes itsseveral objectives of providing an improved rotor having a relativelylightweight shroud of high strength and rigidity fabricated wholly or inthe main of sheet metal components, the strength and rigidity of thesheet metal shroud structure being further fortified by the brazeddovetail mounting of the shroud on the several compressor blade tips andby the alternative forms of turbine blade mounting on the outerperiphery of the shroud.

While only two embodiments of the invention have been shown anddescribed for the purpose of explaining the principals thereof, it willbe apparent to those skilled in the art that many modifications may bemade therein without departing from the scope of the invention, asdefined in the following claims.

We claim:

1. A turbomachine comprising, in combination, a rotor, a first row ofblades mounted on said rotor and extending radially outwardly therefrom,said blades being skewed to the axis of the rotor and each having anumber of aligned spaced projections extending outwardly from the outerend thereof in parallel relation normal to the axis of said rotor, afabricated annular shroud assembly embracing and securing the outer endsof said first blades in equiangular spaced relation to each other, saidshroud assembly comprising an outer band, an inner band, and arectangularly sinuous band intermediate and bonded to said outer andinner bands, said intermediate band having radially andcircumferentially extending webs with the ends thereof extendingtransversely of the shroud, and said inner band having a plurality ofopenings therein disposed to receive the projections of the severalblades intermediate the radial webs of said intermediate band, saidprojections being bonded to said inner and intermediate bands therebyforming a plurality of shroud reinforcing dovetail joints therewith, anda second row of blades mounted on and secured to the periphery of saidshroud, said second row having a plurality of blades secured to andreinforcing said shroud intermediate the ends of said first blades.

2. A rotor element for a turbornachine comprising a rotor disk, a firstrow of blades mounted on said rotor disk and extending radiallyoutwardly therefrom, said blades being skewed to the axis of the rotorand having a number of aligned spaced projections extending outwardlyfrom the outer end thereof in parallel relation normal to the axis ofsaid rotor, a fabricated sheet metal shroud element of corrugated plyconstruction embracing and securing the outer ends of said first bladesin equiangularly spaced relation to each other, said shroud having aplurality of openings therein disposed to receive the projections of theseveral blades intermediate the corrugations of said shroud, and thecorrugations of said shroud and said projections being bonded to form aplurality of shroud reinforcing dovetail joints therebetween.

3. A rotor element as set forth in claim 2, including a second row ofblades mounted on and secured to the periphery of said shroud, saidsecond row having a plurality of blades secured to and reinforcing saidfabricated shroud intermediate the ends of said first blades.

4. A rotor element for a turbomachine comprising a rotor disk, a row ofcompressor blades mounted on said rotor disk and extending radiallyoutwardly therefrom, said blades being skewed to the axis of the rotorand having a number of aligned spaced projections extending outwardlyfrom the outer end thereof in parallel relation normal to the axis ofsaid rotor, a fabricated shroud assembly annularly embracing andsecuring the outer ends of said compressor blades in equiangular spacedrelation to each other, said shroud assembly comprising three concentricradially spaced sheet metal bands and two rectangularly sinuous sheetmetal bands intermediate and bonded to said radially spaced bands, saidsinuous bands having radially and circumferentially extending Webs Withthe ends thereof extending transversely of the shroud, the innermost ofsaid concentric bands having a plurality of openings therein disposed toreceive the projections of the compressor blades intermediate the radialWebs of the innermost sinuous band, a row of hollow turbine bladesmounted on and secured to the periphery of said shroud, said turbineblades having a number of aligned spaced projections extending radiallyinwardly therefrom, the outermost of said concentric bands having aplurality of openings disposed to receive the projections of the turbineblades intermediate the radial Webs of the outermost sinuous band, andsaid compressor and turbine blade projections engaging and being bondedto said sinuous bands thereby forming a plurality of shroud reinforcingdovetail joints therewith.

5. A rotor element as set forth in claim 4, wherein said shroud assemblyincludes two annular end members secured to and supporting the oppositeaxial ends of said concentric and sinuous bands.

6. A rotor eiement for a turbomachine comprising a rotor disk, a row ofcompressor blades mounted on said rotor disk and extending radiallyoutwardly therefrom, said blades being skewed to the axis of the rotorand each having a number of aligned spaced projections extendingoutwardly from the outer end thereof in parallel relation normal to theaxis of said rotor, a fabricated annular shroud assembly embracing andsecuring the outer ends of said first blades in equiangular spacedrelation to each other, said shroud assembly comprising an outer band,an inner band, and a substantially rectangular sinuous band intermediateand bonded to said outer and inner bands, said sinuous band havingradially and circumferentially extending webs with the ends thereofextending transversely of the shroud, said inner band having a pluralityof openings disposed to receive the projections of the several bladesintermediate the radial Webs of said intermediate band, and saidprojections being bonded to said inner and intermediate bands therebyforming a plurality of shroud reinforcing dovetail joints therewith.

7. A rotor element as set forth in claim 6, including a row of turbineblades mounted on and reinforcing the periphery of said shroudintermediate the ends of said first blades, each of said turbine bladescomprising a hollow blade portion and a flanged root element bonded tosaid blade portion and to said outer band.

References Cited in the file of this patent UNITED STATES PATENTS2,398,113 Parrish Apr. 9, 1946 2,771,622 Thorp Nov. 27, 1956 2,801,789Moss Aug. 6, 1957 2,912,222 Wilkes Nov. 10, 1959 2,971,745 Warren et a1Feb. 14, 1961 FOREIGN PATENTS 548,433 Italy Sept. 25, 1956

